The present invention relates in general to amplifiers and, more particularly, to an amplifier having controllable gain based on the output frequency thereof.
Amplifiers are commonly used in electronic circuit design to amplify an input signal over a predetermined frequency range and provide an output signal having increased magnitude. For example, an amplifier operating as a low-pass filter propagates the input signal if its frequency is below a predetermined threshold while higher frequency signals are attenuated based on the frequency response of the filter. The attenuating effect on the high frequency components of the input signal is attributed to losses in the external passive feedback components rather than the amplifier itself. Indeed, the amplifier continues to consume power irrespective of the frequency of the input signal.
Depending on the specific application, the input signal may be valid for only a small portion of the overall period of time that the amplifier is powered on. For example, in voice processing applications, an amplifier may process valid voice data only when the user speaks into a microphone. Yet, the amplifier continues to consume power when just random noise is present at the input. Thus, in some instances, prior art amplifier circuits are known to consume an appreciable amount of power relative to their useful operating period which is undesirable especially in battery driven applications.
Hence, what is needed is an improved amplifier circuit which saves power by reducing its amplification factor when the input signal does not contain valid data.